1. Field of the Invention
This invention relates to a modified multilayer printed wiring board and a modified method for manufacturing the multilayer printed wiring board, and more particularly relates to a multilayer printed wiring board having high density wiring and a method for manufacturing the multilayer printed wiring board having high density wiring.
2. Description of the Related Art
FIG. 8A to FIG. 8E show an exemplary process for manufacturing a conventional multilayer printed wiring board, and the process for manufacturing the conventional multilayer printed wiring board will be described herein under with reference to FIG. 8A to FIG. 8E.
At first, as shown in FIG. 8A, copper foils are formed on both sides of an insulating board to form a plurality of laminates 1 that are not conductive between both sides. Subsequently as shown in FIG. 8B, a via hole la is formed on each laminate, and the laminate becomes conductive between both sides by, for example, plating on the via hole.
Subsequently as shown in FIG. 8C, a plurality of laminates 1 are laminated by use of a bonding member 2 consisting of prepreg. Then, a through hole 3 that passes through the plurality of laminates 1 is formed as shown in FIG. 8D. To ensure electrical connection between the laminates, for example, copper foils 4 or the like is formed by plating on the surface of the laminates and the through hole 3. Finally, the copper foils on the surfaces of the laminates are patterned desiredly to complete a multilayer printed wiring board 5.
FIG. 9A to FIG. 9E show another conventional process for manufacturing a multilayer printed wiring board, a method for manufacturing a multilayer printed wiring board will be described herein under with reference to FIG. 9A to FIG. 9E. The manufacturing method shown in FIG. 9A to FIG. 9E is a method so-called as build-up method.
At first, as shown in FIG. 9A, through holes 7 are formed on a laminate 6 comprising an insulating board, and the surface of the through holes 7 is plated. Then, insulating layers 8 are formed on both sides of the laminate 6 as shown in FIG. 9B. Subsequently as shown in FIG. 9C, via holes 9 are formed on the insulating layers 8, and the via holes 9 are plated. By repeating the processes shown in FIG. 9B to FIG. 9D, a multilayer printed wiring board 10 shown in FIG. 9D is formed. It is possible to form high density wiring because wirings are intersected each other on the same plane as described hereinabove.
However, the multiplayer printed wiring board and the manufacturing method thereof described hereinabove are involved in the problem as described hereafter.
In the method for manufacturing a multilayer printed wiring board shown in FIG. 8A to FIG. 8E, it is required to form a through hole 3 that passes through all the laminates 1 in order to render arbitrary laminates 1 conductive therebetween. As the result, it is difficult to realize a high density multilayer printed wiring board, and the less freedom of high density wiring of a multilayer printed wiring board 5 is the problem.
Furthermore, in the method for manufacturing a multilayer printed wiring board shown in FIG. 9A to FIG. 9E, it is required to form a plurality of insulating layers 8 and to plate, and such a long manufacturing process results in poor yield and the poor yield is the problem.
Recently, a method for forming a multilayer printed wiring board (B2it(trademark)) (Buried Bump Interconnection Technology) in which a projection member is formed with conductive paste and prepreg is penetrated, and a method for forming a multilayer printed wiring board (ALIVH(trademark)) (Any Layer IVH Structure Printed Wiring Board) in which a through hole is formed on prepreg and a projection member is inserted into the through hole are presented.
However, the so-called B2it(trademark) is involved in a problem that the thickness of a printed wiring board is restricted because the projection member is formed of conductive paste. In detail, it is required to use a large projection member to render the insulating layer thick and the large projection member is disadvantageous for high density wiring. On the other hand, it is required to render the insulating layer thin if the bump is small.
ALIVH(trademark) is also involved in a problem that the resistance value in the through hole is large because conductive paste connects between layers. Both in B2it(trademark) and ALIVH(trademark), conductive paste that migrates along fibers that form the insulating layer is also a problem.
The present invention has been accomplished to solve the above-mention problems, and provides a multilayer printed wiring board having high density wiring to be formed easily and a manufacturing method thereof.
According to one aspect of the present invention, the above-mentioned object is achieved by applying a method for manufacturing a multilayer printed wiring board formed by laminating a plurality of laminates comprising a step for forming a conduction hole on a laminate comprising an insulating board having both sides on which conductive films are formed, a step for electrically connecting between both sides of the above-mentioned laminate through the above-mentioned conduction hole and planarizing the surface, a step for patterning the above-mentioned conductive film desiredly and forming a projection member at a desired position of the above-mentioned conductive film, a step for laminating bonding members having a through hole to which the above-mentioned projection member is inserted, which is served for bonding between the above-mentioned laminates, and the above-mentioned laminates alternately with insertion of the above-mentioned projection member into the above-mentioned through hole, and a step for press-molding the above-mentioned laminated laminates and bonding members with heating.
According to the structure of the above aspect, a multilayer printed wiring board is manufactured by applying a process comprising a step for alternately laminating laminates having conductive films in the form of desired pattern on which a projection member is formed and bonding members on which a through hole is formed, and a step for press-heat-molding a plurality of laminates and bonding members that have been laminated alternately. Electrical connection between arbitrary laminates is formed by connecting a projection member consisting of metal to a conductive film.
Laminates are laminated not in one after another fashion, but a laminate and a projection member are laminated previously and heat-press-molded in one step to manufacture a multilayer printed wiring board. Furthermore, laminates to be used for a multilayer printed wiring board are manufactured separately and then laminated. Thereby, only non-defective laminates are used for manufacturing. Because the projection member consists of metal, the length can be adjusted arbitrarily, and the resistance value between laminates is small when the projection member is connected to the conductive film consisting of metal.
According to another aspect of the present invention, the above-mentioned object is achieved by applying a multilayer printed wiring board formed by means of a laminating process comprising a step for forming a conduction hole on a laminate comprising an insulating board having both sides on which conductive films are formed, a step for electrically connecting between both sides of the above-mentioned laminate through the above-mentioned conduction hole and planarizing the surface, a step for patterning the above-mentioned conductive film desiredly and forming a projection member at a desired position of the above-mentioned conductive film, a step for laminating bonding members having a through hole to which the above-mentioned projection member is inserted, which is served for bonding between the above-mentioned laminates, and the above-mentioned laminates alternately with insertion of the above-mentioned projection member into the above-mentioned through hole, and a step for press-molding the above-mentioned laminated laminates and bonding members with heating.
According to the structure of the above aspect, laminates, each of which has a conductive film having a predetermined pattern on which projection members are formed, and bonding members, each of which has through holes, are laminated alternately and a plurality of laminated laminates are subjected to press-heat, molding. A metal projection member is electrically connected to a conductive film to electrically connect between arbitrary laminates. A multiplayer printed wiring board is formed not by laminating laminates one after another but by molding laminates and projection members at a time in the present invention.
Because the projection member consists of metal, the length of the projection member can be adjusted arbitrarily, and the resistance value between laminates is reduced when the conductive film consisting of metal is connected to the projection member. As the result, the freedom of wiring is improved and the high-density wiring is realized by applying the multilayer printed wiring board of the present invention.